1. Field of the Invention
This invention relates to a device for automatically applying tension to a drive belt used in conjunction with rotating accessories mounted at the front of a vehicular engine.
2. Disclosure Information
Flexible power transmission members, such as roller chains and belts, have been used with automotive engines for many years. With either type of flexible member, it is usually desirable to maintain the tension of the member at a level sufficient to prevent slipping of the chain or belt over the various sprockets or pulleys upon which the flexible member is trained.
The slippage of chains used to drive an engine's valve gear can have disastrous results if the engine is not designed to be free-wheeling. Accordingly, the need for chain tensioning under such circumstances has been recognized for many years. U.S. Pat. No. 1,701,820 to Morse discloses a rotary chain tensioning mechanism mounted within the chain case of an engine. U.S. Pat. No. 3,136,170 to Murray discloses yet another type of spring driven chain tensioner dismounted by means of a bracket within the chain case of an engine. Finally, Swiss Patent Publication 279415 discloses a hydraulically controlled chain tensioner in which engine oil pressure acts upon an arbor upon which a tensioning sprocket is mounted.
The slipping of accessory drive belts used for the purpose of providing power to such engine accessories as a power steering pump, air conditioning compressor, and an alternator, will usually not produce disastrous results because such accessories are most often not required to operate at full rated output. Drive belt slippage will, however, occasion complaints by the driver of a vehicle should the slippage be accompanied by undesirable squealing or chirping noises. For this reason, inter alia, automotive designers have striven to avoid slipping of accessory drive belts
U.S. Pat. No. 4,031,761 to Fisher et al., U.S. Pat. No. 4,145,934 to Sragal, U.S. Pat. No. 4,285,676 to Kraft, U.S. Pat. No. 4 351,636 to Hager, U.S. Pat. No. 4,392,840 to Radocaj, U.S. Pat. No. 4,557,709 to St. John, U.S. Pat. No. 4,822,322 to Martin, U.S. Pat. No. 4,908,007 to Henderson, and U.S. Pat. No. 4,934,988 to Kawamura et al, all , disclose accessory drive belt tensioning devices which are essentially added on to an engine by bolting the device to the front structure of the engine. Such devices suffer from a couple of different drawbacks. First of all, because the tensioning device is secured in most cases by means of a bracket to the engine, the securing structure generally lacks rigidity and as a result will have vibration characteristics which in many cases are less than optimal. Secondly, bracketry increases the weight, cost, and package volume of the tensioning devices, as opposed to a device according to the present invention, in which the tensioner is integrated into the front cover of an engine. It is thus an object of the present invention to provide an engine accessory drive tensioner which has superior functional characteristics in terms of its resistance to unwanted vibration.
It is another object of the present invention to provide an accessory drive tensioner which is of low mass.
It is yet another object and advantage of the present invention that a tensioner according to this invention will have a smaller package volume as compared to known tensioners.
It is yet another advantage of the present invention that a tensioner according to this invention will be less costly than known prior art tensioners.
Other objects, features and advantages of the present invention will become apparent to the reader of the specification.